The present invention relates to a cleaning liquid for semiconductor devices used in the process for producing semiconductor integrated circuits, and more particularly to a cleaning liquid for semiconductor devices used for removal of resist residues left remaining after dry etching. 2. Description of the Related Arts
Semiconductor integrated circuits are produced in accordance with the following procedures: an inorganic substrate is coated with a photoresist; patterns are formed on the photoresist by exposure of light followed by development; the patterned photoresist is used as a mask, and portions of the inorganic substrate not masked by the photoresist are dry etched with a reactive gas and then ashed; and resist residues (protective deposit films) left remaining on the inorganic substrate are removed from the inorganic substrate. A gas containing chlorine is generally used to dry etch the photoresist coated on the inorganic substrate. Resist residues are formed by the reaction of the photoresist with the reactive gas containing chlorine during the dry etching. Protective deposit films left remaining on the inorganic substrate cause disconnection and abnormal wiring, and various troubles arise. Therefore, complete removal of the protective deposit films is desired.
Alkaline cleaning liquids have heretofore been used as the liquid for removing resist residues. Examples of the alkaline cleaning liquid include a cleaning liquid comprising an additional product of ethylene oxide to an alkanolamine or a polyalkylenepolyamine, a sulfone compound, and a glycol monoalkyl ether (Japanese Patent Application Laid-Open No. Showa 62(1987)-49355) and a cleaning liquid comprising dimethylsulfoxide as the main component and a diethylene glycol monoalkyl ether and an organic hydroxy compound containing nitrogen as other components (Japanese Patent Application Laid-Open No. Showa 64(1989)-42653). However, the above cleaning liquids become alkaline during the use because of dissociation of the amine caused by absorbed water. When cleaning is conducted with water without using an organic solvent such as an alcohol after the removal of the resist residues, water used in the cleaning becomes alkaline. This accelerates corrosion of aluminum which is frequently used as the wiring material in the formation of fine circuits. Therefore, the above cleaning liquids are not preferable for use in the recent working of fine structures which require rigorous precision.
Cleaning liquids for semiconductor devices comprising an aqueous solution containing a fluorine compound, an organic solvent, and a corrosion inhibitor have recently been used as a cleaning liquid which shows an excellent ability to remove resist residues and can be used conveniently (Japanese Patent Application Laid-Open Nos. Heisei 7(1995)-201794 and Heisei 8(1996)-20205).
However, the condition of dry etching continues to become severer. For example, a gas containing fluorine is added to a gas containing chlorine for dry etching, and a high density plasma is used for dry etching. This change in the condition causes further chemical change in the resist residues, and the above cleaning liquids for semiconductor devices cannot achieve complete removal of the resist residues.
When an alkali metal such as sodium and potassium is present in a cleaning liquid, the metal is adsorbed on the surface of a substrate. When a device is formed on the substrate in this condition, a problem arises in that the properties of the device tend to deteriorate even at a low temperature because of the presence of mobile ions which are derived from the alkali metal and move within the device, and thus yield of the device tends to decrease.
As described above, a cleaning liquid which can remove resist residues left remaining after dry etching and ashing in the wiring step in the production of semiconductor integrated circuits rapidly and completely at a low temperature and does not corrode wiring materials has been desired.